Explanation:

CO is the colorless, odorless, toxic gas produced due to incomplete burning of wood. Incomplete combustion will occur when there is not enough oxygen to allow the fuel to react completely to produce carbon dioxide and water. ... For most fuels, such as diesel oil, coal or wood, pyrolysis occurs before combustion. The short answer is incomplete combustion. In order to get something to burn you need three things, all in the proper combination: fuel (such as wood, oil or gas), oxygen and heat. ... As a result, you are often left with unburned fuel, particulates, ash, carbon monoxide and nitrogen oxides.